04 005 Porcelain veneers Part II by qpNqZTzM

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									                                                                                                         Naval Postgraduate Dental School

                       Clinical Update                                                                     National Naval Dental Center
                                                                                                               8901 Wisconsin Ave
                                                                                                          Bethesda, Maryland 20889-5602


Vol. 26, No. 5                                                                                                                          May 2004
                                      Porcelain veneers – part II: preparation and delivery
                             Lieutenant Yaohsien Peng, DC, USNR, Captain Blaine Cook, DC, USN, and
                                                  Captain Dean Beatty, DC, USN
Introduction
Porcelain Veneers Part I, July 2003, reviewed the evaluation and                  In preparing diastema closure, the interproximal preparation is
treatment planning phases of porcelain veneer restorations. Part II               extended through the contact toward the lingual. The greater
will address clinical techniques used in tooth preparation, delivery,             the space to be closed, the farther the preparation must be
and the post-operative phases of treatment.                                       carried to the lingual. It is also important to extend the
                                                                                  interproximal preparation subgingivally to recontour the
Traditional preparation design                                                    papilla. This type of preparation must be provisionalized to
Traditional veneer preparation is a conservative reduction of tooth               reduce sensitivity and prevent migration (1).
structure consisting of 0.5mm facial reduction with interproximal
finish lines facial to the contact area. Because all prepared surfaces        Material options
are generally in enamel and contacts are left undisturbed, the need            Feldspathic porcelain. Traditionally, ceramic veneers are
for temporization is minimized and the potential for pulpal                      fabricated by layering feldspathic porcelain onto a refractory
involvement is significantly reduced. Supragingival veneer margins               die or platinum foil (3).
avoid the risk of irritation to periodontal tissues (1).                       Densely sintered high-purity magnesium oxide base coping, e.g.
                                                                                 In-Ceram Spinell. The core is more translucent than the
Preparation Procedure:                                                           traditional In-Ceram but does not posses the same flexure
1. Retract gingival tissue if necessary.                                         strength. It can be veneered with feldspathic porcelain but is
2. Make a series of facial depth cuts by either using round carbide              not necessary.
    burs, or BrasselerTM or NixonTM depth cutters. Reduction of 0.5            Heat-pressed ceramic material, e.g. IPS Empress. Leucite-
    mm is usually adequate and should follow the anatomic                        reinforced feldspathic porcelain has improved flexural strength,
    contours of the teeth.                                                       fracture resistance, and excellent marginal adaptation. It can
3. Place a “long chamfer” margin with an obtuse cavosurface                      also be veneered with feldspathic porcelain.
    angle, which exposes the enamel prism ends at the margin for
    better etching. The margin should closely follow the gingival             Veneer delivery procedures
    crest.                                                                    Preliminary inspection
4. Place the preparation margin labial to the proximal contact area            Examine veneers under magnification.
    to preserve it in enamel.                                                  Check fit of veneers on dies by first trying veneers one-at-a-
5. Do not reduce the incisal edge if possible; this helps support the              time and then all together.
    porcelain and makes chipping less likely. If the incisal length is         Clean the restorations thoroughly in water with ultrasonic
    to be increased, the tooth should be reduced to allow for a                    agitation.
    minimum of 1.5mm of porcelain.                                            Tooth Preparation
6. Avoid undercuts and visualize the path of insertion because an              Thoroughly clean the preparations, making sure all provisional
    undercut will prevent placement of the veneer.                                 luting agents are removed.
7. Connect depth cuts and margins. To prevent areas of stress                  Try-in restorations with water, first one-at-a-time and then all
    concentration in the porcelain, ensure the tooth preparation is                together. Verify fit, shade, and insertion sequence.
    free of sharp angles. All prepared surfaces should be rounded             Color Check and Characterization
    and smoothly flowing.
                                                                               Place one laminate in position with water or glycerine and then
                                                                                   compare it to the shade tab selected. If the laminate appears
Alternate preparation designs
                                                                                   dark, then a lighter colored resin cement should be selected.
 Ultraconservative preparation design is more conservative than                   Utilize color-keyed try-in pastes to evaluate and select the
    the traditional veneer preparation, which can result in dentin                 appropriate shade (4).
    exposure in the cervical areas. This preparation design
                                                                               Veneers can also be characterized externally using a special
    advocates cervical reduction of 0.3mm and midfacial reduction
                                                                                   laminate low-fusing color system, which fuses at approximately
    of 0.3mm to 0.5mm, which takes into account the mean thick-
                                                                                   1,400F. The laminate can also be supported with an instant
    ness of enamel (2).
                                                                                   investment, which when set facilitates coloring and glazing with
 Extending traditional veneer preparation is appropriate for
                                                                                   any conventional system (4).
    situations requiring hidden margins, or increased retention. In
                                                                              Cementation
    this design, proximal margins are extended into or through the
                                                                               Use rubber dam isolation or displacement cord, cotton rolls,
    contacts and the gingival margins are placed slightly
                                                                                   and cheek retractors.
    subgingival. It is indicated for malaligned teeth, discoloration,
                                                                               Clean the teeth with pumice. Wash and dry.
    black space closure, veneers adjacent to crowns, replacing
    restoration or wrapping an existing restoration, and diastema
    closure (1).
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    Check with the dental laboratory to see if the fabricated veneers              There is also an increase in papillary bleeding on probing in
     were etched. If not, etch the internal surface of the veneer with              25% of restored teeth with subgingival restoration margins (7).
     hydrofluoric acid for 5 minutes. Rinse and dry.                               Subgingivally placed margins of dental restorations are
 Silane is painted onto the etched porcelain to enhance the                        associated with pathologic alteration of the adjacent gingiva;
     adhesive properties of the resin. Allow to dry for one minute                  the greater the marginal inaccuracy of the restoration, the
     and gently air-dry the veneer surface (4, 5).                                  greater the permanent damage to the periodontal tissue (7).
 Place a Mylar matrix strip, dead soft metal matrix, or plumber’s
     teflon tape interproximally to protect adjacent teeth.                     Maintenance
 Etch the enamel with 37% phosphoric acid for 30 seconds.                       Resin polymerization takes at least 72 hours to complete.
     Rinse thoroughly and dry.                                                     During this early phase, hard and extremely hot or cold food,
 Following the manufacturer’s instructions for cementing                          alcohol and medicated mouthwashes should be avoided. (4)
     veneers, apply bonding agent to etched enamel and etched,                   Patients will have a period of adjustment for the first two weeks
     silanated veneer surface but do not light cure.                               as they get used to the "new" teeth that changed in size and
 Apply light cure composite resin luting agent to the restoration.                shape.
     Be careful to avoid trapping air.                                           Patients should be instructed to use a soft toothbrush with
 Position the restoration gently, seating veneer from incisal to                  rounded bristles, and to floss daily.
     gingival. Remove excess luting agent with an instrument.                    Patients should also avoid biting on hard objects/food with
 Hold the restoration in place while light-curing the resin. Do                   restored teeth.
     not press on the center of veneers; they may flex and break.                Routine cleanings are recommended at least every four months
 Remove excess cement before full cure being careful not to pull                  with a hygienist. Ultrasonic scalers and air abrasion systems
     cement out from veneer margin leaving a defect.                               should be avoided.
 Light cure for 40 seconds from several directions for 2-3                      A hard night guard is useful to decrease the potential for
     minutes cumulative cure time per veneer.                                      fracture of the laminate and excessive wear of the opposing
Finishing                                                                          arch. A soft acrylic mouth guard should be used for any form
 Remove resin flash with a scalpel or sharp curette.                              of contact sports.
 It is important to realize that the unsupported porcelain veneer
     should never be contoured until bonding is completed.                      References
 Finish accessible margins and occlusion with fine diamonds,                   1. Rouse JS. Full veneer versus traditional veneer preparation: a
     using water spray. Use finishing strips for the interproximal              discussion of interproximal extension. J Prosthet Dent. 1997 Dec;
     margins.                                                                   78(6): 545-9.
 Polish adjusted areas with an intra-oral porcelain polishing                  2. Rouse J, McGowan S. Restoration of the anterior maxilla with
     system (rubber wheels or points, diamond polishing paste, etc.)            ultraconservative veneers: clinical and laboratory considerations.
     Caution: for pressable systems, e.g. Empress, the color is on              Pract Periodontics Aesthet Dent. 1999 Apr;11(3):333-9.
     the surface and can be polished away.                                      3. Zhang F, Heydecke G, Razzoog ME. Double-layer porcelain
                                                                                veneers: effect of layering on resulting veneer color. J Prosthet
Seating sequence in multi-unit case                                             Dent. 2000 Oct;84(4):425-31.
Start with the two central incisors. It is essential that the veneers of        4. Garber DA, Goldstein RE, Feinman RA. Porcelain Laminate
the central incisors be positioned correctly. The two lateral incisors          Veneers. Quintessence Publishing Co. 1988: 90-98.
are then seated, one at a time, to accommodate any discrepancies in             5. Kamada K, Yoshida K, Atsuta M. Effect of ceramic surface
overall fit (4). There are numerous opinions about the cementation              treatments on the bond of four resin luting agents to a ceramic
sequence of the remaining veneers. Minor adjustments made on                    material. J Prosthet Dent. 1998 May;79(5):508-13.
posterior teeth can be accomplished without jeopardizing esthetics.             6. Dumfahrt H, Schaffer H. Porcelain laminate veneers. A
                                                                                retrospective evaluation after 1 to 10 years of service: Part II-
Factors influencing veneer failure                                              Clinical results. Int J Prosthodont. 2000 Jan-Feb;13(1):9-18.
 Adhesion of the veneer seems to be the most important factor to               7. Christgau M, Friedl KH, Schmalz G, Resch U. Marginal
    reduce the compressive and tensile stresses in the veneer.                  adaptation of heat-pressed glass-ceramic veneers to dentin in vitro.
    Contamination during bonding significantly decreases the bond               Oper Dent. 1999 May-Jun;24(3):137-46.
    strength of the porcelain veneers.
                                                                                LT Peng is a third year resident in the Prosthodontics Department.
 Higher porcelain veneer failure rates have been observed when
                                                                                Captain Cook is the Chairman of the Operative Dentistry
    the gingival margin is located on dentin. Today's dentin
                                                                                Department and Captain Beatty is a faculty member in the
    bonding agents are improved over previous generations but no
                                                                                Prosthodontics Department at the Naval Postgraduate Dental
    long-term data exist indicating the expected longevity of
                                                                                School.
    bonded dentin margins (6). Ideally all veneer margins should
    be on enamel. When cervical margins must be on dentin,
                                                                                The opinions and assertions contained in this article are the private
    utilize highly filled, viscous resin cements and dentin bonding
                                                                                ones of the authors and are not to be construed as official or
    agents of the latest generation to achieve greatest longevity (6).
                                                                                reflecting the views of the Department of the Navy.
 Patients who smoke increase their risk of veneer failure due to
    staining at the veneer margins (6).
                                                                                Note: The mention of any brand names in this Clinical Update does
 There is an increase in gingival recession in 31% of the
                                                                                not imply recommendation or endorsement by the Department of the
    patients, which ranged from 0.1 to 0.5mm. 88% of the
                                                                                Navy, Department of Defense, or the U.S. Government.
    recession is localized in teeth where the margin is subgingival.
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